1. Field of the Invention
The present invention relates to a ball screw with an oil-storage unit, and more particularly to an oil storage unit which can be quickly assembled onto the ball screw to provide an automatic and continuous self-lubricating function to the ball screw.
2. Description of the Prior Art
Ball screw is used for motion transmission by taking use of the relative motion between its nut and screw shaft, the movement of the nut is realized by the rolling motion of the rolling elements between the nut and the screw shaft, so that the ball screw has a high efficiency of mechanical transmission. However, if the ball screw has not been lubricated enough for a long period of time, it may result in an increase in friction between the nut and the screw shaft, thus accelerating the abrasion of the ball screw. Hence, self lubricating function of a linear guideway has become more and more important. So far, the self-lubricating methods are generally divided into two types: the first method is to fix the lubricating system at both ends of the nut, lubricating oil is stored in the lubricating system, and then an oil absorbing material is used to smear the lubricating oil to the surface of the screw shaft. Another method is to fix an oil-absorbing material made wiper at either side of the nut, lubricating oil is stored in the oil absorbing material, and the oil absorbing material keeps contacting the surface of the screw shaft, so as to lubricate the teeth of the screw shaft, so that the rolling elements can be lubricated indirectly when rolling through the teeth of the screw shaft.
Both of these two methods are to lubricate the teeth of the screw shaft, and then the rolling elements only can be lubricated indirectly by the lubricating oil left on the screw shaft when rolling through the teeth of the screw shaft, therefore, the rolling elements may not be evenly lubricated, and it will cause waste of lubricating oil. In addition, both of the above-mentioned oil absorbing material and the oil-storage unit only can store a small amount of oil, so the lubrication effect will not last for a long time. However, the service life of the linear guideway is 5-10 years or above, as a result, the rail of the linear guideway will be spoiled ahead of its service life time, due to lack of lubrication. On the other hand, it will be time-consuming and difficult when the oil absorbing material and the oil-storage unit are assembled to or disassembled from the sliding block since they are fixed by screwing method.
FIG. 14 shows another conventional ball screw 2 with an oil-storage unit 1, wherein the oil-storage unit 1 is formed with an oil feeding hole 11 in communication with an oil-storage space 12. A connector 3 formed with an oil feeding hole 301 has one end connected to the nut 201 and another end connected to the oil feeding hole 11 of the oil-storage unit 1, so that lubricant oil can be transported to the nut 201 by the connector 3. However, the connector 3 cannot be positioned by itself and needs to be fixed by using a spring 4 to push the end of the connector 3, and then a screw 5 is used to fix the spring 4, rendering this oil-storage unit 1 relatively inconvenient to assemble and disassemble.
FIG. 15 shows another conventional ball screw shaft 90 on which is movably disposed a reciprocating platform 91, a motor 93 controlled by a numerical control device 92 rotates the screw shaft 90 so as to cause reciprocating motion of the reciprocating platform 91 with respect to the screw shaft 90. The method for lubricating the screw shaft 90 is such that the lubricant oil is pumped by a pump 94 from an oil-storage unit 96 to an oil feeding hole 951 of a connecting pipe 95, and then the lubricant oil drops to an oil receiving hole 901 of the screw shaft 90 to lubricate the screw shaft 90. The oil-storage unit 96 and the connecting pipe 95 are independent structures from the screw shaft 90 and therefore are inconvenient to assemble and space consuming. Furthermore, the lubricant oil is likely to leak out and cause environmental contamination if the oil-storage unit 96 and the connecting pipe 95 are not well designed and assembled.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.